GCN Circular 40357
Subject
GRB 250504A: Swift-BAT refined analysis
Date
2025-05-06T02:54:01Z (17 hours ago)
From
Mike Moss at NASA GSFC <mikejmoss3@gmail.com>
Via
Web form
D. M. Palmer (LANL), S. D. Barthelmy (GSFC),
R. Gupta (GSFC), H. A. Krimm (NSF),
S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa),
C. B. Markwardt (GSFC), M. J. Moss (GSFC),
T. Parsotan (GSFC), D. Sadaula (GSFC/UMBC),
T. Sakamoto (AGU) (i.e. the Swift-BAT team):
Using the data set from T-239 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 250504A (trigger #1310284)
(Moss, et al., GCN Circ. 40343). The BAT ground-calculated position is
RA, Dec = 269.605, -40.345 deg which is
RA(J2000) = 17h 58m 25.3s
Dec(J2000) = -40d 20' 41.8"
with an uncertainty of 1.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 98%.
The mask-weighted light curve shows a complex light curve with several pulses.
T90 (15-350 keV) is 52.39 +- 2.31 sec (estimated error including systematics).
The time-averaged spectrum from T-2.96 to T+55.10 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.27 +- 0.08. The fluence in the 15-150 keV band is 2.3 +- 0.1 x 10^-06 erg/cm2.
The 1-sec peak photon flux measured from T+7.70 sec in the 15-150 keV band
is 1.6 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence
level.
The results of the batgrbproduct analysis are available at
https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1310284